[Spontaneous and induced metamorphosis inXenopus larvae at low temperature]

Area of Science:

• Developmental Biology
• Endocrinology
• Amphibian Research

Context:

• Premetamorphic Xenopus laevis larvae exhibit temperature-dependent mortality and metamorphic responses.
• Temperature significantly impacts the timing and progression of amphibian metamorphosis.

Purpose:

• To investigate the effect of low temperatures on spontaneous metamorphosis in premetamorphic Xenopus larvae.
• To determine the role of the hypothalamic center and larval tissue sensitivity in cold-induced metamorphic inhibition.

Summary:

• Mortality in premetamorphic Xenopus larvae is unaffected by temperatures down to 8.5°C but increases sharply below this threshold.
• Complete inhibition of spontaneous metamorphosis occurs at 10°C only in premetamorphic larvae; later stages (beyond 56) experience delayed changes.
• Thyroxine and Thyroid-Stimulating Hormone (TSH) can still elicit metamorphic responses in cold-arrested larvae, indicating that larval tissues retain their sensitivity to these hormones.
• The blockage of spontaneous metamorphosis at low temperatures is attributed to the inhibition of the hypothalamic center, not a diminished responsiveness of larval tissues to thyroxine.

Impact:

• This study elucidates the critical role of temperature regulation in amphibian development and metamorphosis.
• Findings suggest that the hypothalamic-pituitary-thyroid axis is particularly sensitive to cold stress during specific developmental windows.
• Provides insights into the neuroendocrine control of metamorphosis and potential disruptions due to environmental changes.